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Declare compliance with the U32 bit region interface for fixed-point data types with 33 or more bits

The ssFxpSetU32BitRegionCompliant function can be ignored. This function no longer has any impact on the memory layout for inputs and outputs. The memory layout introduced in R2008a is always used.


extern ssFxpSetU32BitRegionCompliant(SimStruct *S,
                          int Value)



SimStruct representing an S-function block.

  • 1 declare compliance with memory footprint for fixed-point data types with 33 or more bits.


Before R2020a: This function declares compliance with the Fixed-Point Designer™ bit region interface for data types with 33 or more bits. The memory footprint for data types with 33 or more bits varies between MATLAB® host platforms and might change between software releases. To make an S-function robust to memory footprint changes, use the U32 bit region interface. You can use identical source code on different MATLAB host platforms and with any software release from R2008b. If the memory footprint changes between releases, you do not have to recompile U32 bit region compliant S-functions. To make an S-function U32 bit region compliant, before calling any other Fixed-Point Designer API function on data with 33 or more bits, you must call this function as follows:

If an S-function block contains a fixed-point data type with 33 or more bits, call this function in mdlInitializeSizes().


The Fixed-Point Designer software assumes that S-functions that use fixed-point data types with 33 or more bits without calling ssFxpSetU32BitRegionCompliant are using the obsolete memory footprint that existed until R2007b. Either redesign these S-functions or isolate them using the library fixpt_legacy_sfun_support.


To use this function, you must include fixedpoint.h and fixedpoint.c. For more information, see Structure of the S-Function.



Version History

Introduced in R2009a